Conventionally, packaging films are used to seal and protect products inside a container, or simply inside a film-formed package, from exposure to the atmosphere. In order to provide the necessary barrier and sealing properties, materials such as polyolefins, PVDC and polyethylene terephthalate have been used in the past. However, such materials are not usually compostable and there is a consequent need to provide compostable packaging films. However, it has proved difficult to find such films which have suitable barrier and/or sealing properties, and it is an object of the invention to find a solution to this problem. It is a particular object of the invention to find such a solution which does not add unreasonable cost to the manufacturing process and which does not adversely affect to an unreasonable degree other desirable properties of the film, such as optical and mechanical properties, for example.
EP-A-2141191 discloses a composite package comprising a layer of a biodegradable, compostable copolyester extrusion coated onto the surface of a biodegradable compostable cellulose film. However, the applied coatings are relatively thick and it would be desirable to provide thinner coatings whilst maintaining acceptable seal strengths.
US 2007/0184220 discloses a range of coat weights of biopolymers forming part of thicker, laminated structures for carton-board rather than filmic applications.
WO 99/01278 discloses paper-based laminates having low coat weights of a polyester amide extrusion coated thereon.
Other, thicker laminated paper-based materials with various coatings are disclosed in WO 00/01530 and in WO 2009/064942.
WO 2009/024812 discloses a sealable, peelable film comprising a coating on a cellulosic substrate of a coating composition comprising a copolymer of lactic acid and caprolactone.